The present invention relates generally to a cooling arrangement.
More particularly, the invention relates to a cooling arrangement for rolled materials, such as wires, rods and the like.
On completion of the final rolling step these materials, especially wire, must be chilled rapidly and repeatedly; such chilling must be as uniform and intensive as possible over the entire surface area of the workpiece. Moreover, to obtain the desired effect it is necessary--as explained e.g. in U.S. Pat. No. 1,211,277--to remove the cooling fluid quickly after each chilling step so that the heat at the core of the workpiece can quickly raise the temperature of the workpiece surface again.
To effect such chilling it is known to use tubes through which the workpiece, such as wire, travels to be contacted on one tube section with a cooling fluid (e.g. water) which is rapidly withdrawn at another tube section. It is also known to arrange several such tubes one behind the other, to provide an installation in which the wire can be repeatedly chilled and allowed to reheat (due to its core heat) intermediate the chilling stations.
One problem with this known state of the art is that it is not well suited for the production of special high-quality wires, for example wires in which a core with fine-striped perlite and with an outer martensite layer of a specific thickness is to be produced. The known arrangements permit a rapid application of the cooling medium to the wire surface, but do not permit a rapid enough subsequent withdrawal of the cooling medium out of contact with the surface. This, however, is a major requirement when it is desired to produce certain steels of uniform high quality, since to obtain these it is necessary to subject the workpiece to rapid chilling (to produce a maximum temperature difference between the workpiece core and the workpiece surface) and thereafter to assure equally rapid temperature equalization between the core and the workpiece surface due to reheating of the surface by the heat of the core.
In the known cooling arrangements the length of the path portion in which the workpiece is first contacted with cooling fluid is quite substantial; this means--especially if the workpiece coming from the final rolls of the mill travels at a high rate per unit time--that the length of the path portion in which the cooling fluid is subsequently conducted away from the workpiece must also be very long, since otherwise it is impossible to remove all of the cooling fluid. Because of this, the known arrangements are not suitable under the special circumstances outlined above, since the duration of contact between the cooling medium and the workpiece is too long to permit the necessary rapid chilling and equally rapid reheating (due to the core heat) of the workpiece surface.
Moreover, the known arrangements do not permit contacting of the workpiece over a substantial length with an adequate quantity of cooling fluid, since large portions of the path travelled by the workpiece are shielded by long workpiece-guiding tubes which prevent access of the cooling fluid to the workpiece. Hence, only small and inadequate quantities of cooling fluid can be sprayed onto the workpiece through a nozzle at one end of the respective guide tube--and the thus admitted cooling fluid can moreover be removed only through a few small bores at the other end of the guide tube. Since these bores necessarily create a flow resistance for the cooling fluid, they increase the dwell time of the fluid (i.e., the time for which it remains in contact with the workpiece surface). Thus, neither the initial chilling nor the subsequent reheating of the workpiece can take place fast enough to meet the requirements which are made when steel of uniform high quality is to be produced.
Finally, the known arrangements have still a further disadvantage, in that the ends of workpieces (especially wires) travelling through the guide tubes tend to become caught in the bores or slots provided in the guide tubes for evacuation of the cooling fluid. This leads inevitably to malfunctions and consequently to uneconomical machine down-time.
Another prior art arrangement is known from German Patent DE-PS No. 557,455. Here, the workpieces are guided through a housing which is provided with several annular water-stripping elements. Because of the guidance of the workpieces these elements must be arranged in close succession so that the cooling water can be sprayed only onto short increments of the workpiece surface. Sudden chilling of the workpiece surface over a substantial length of the same is not possible, nor can uniform chilling be obtained by the disclosed spraying action. This arrangement is, therefore, suited for its own specific purpose but not for treating workpieces of the type outlined above, especially since immediately downstream of ech of the stripping elements another cooling step takes place so that due to the close spacing of these elements, the requisite reheating of the workpiece from the core heat cannot occur.